Correction of spinal deformities, such as scoliosis, kyphosis, and spinal instability, has utilized external traction apparatus, external bracing devices, external frameworks that extend inwardly of the patient's body and attach to vertebrae as taught by Latypov in U.S. Pat. No. 4,112,935, and apparatus for implantation into the patient's body for orthesis and/or prosthesis.
Implantation apparatus has included apparatus for anterior implantation and apparatus for posterior implantation.
Another implantation has included that known by the trade name Dwyer in which screws with transversely disposed holes in the heads thereof are anteriorly screwed into the body of various ones of the vertebrae. A wire or cable is threaded through the holes in the screw hands and tensioned to produce a compressive and stabilizing force.
Posterior implantation apparatus has included that taught by Roaf, U.S. Pat. No. 3,565,066, in which a rigid member bridges a scoliotic, kyphotic, or lordotic curve and hooks are disposed orthogonally to the rigid member and are used to hookingly engage and to move individual vertebrae toward the rigid member.
Posterior implantation apparatus has also included Nissinen, U.S. Pat. No. 4,078,559, in which a rigid and longitudinally extendable rod is used to tension a pair of flexible rods that are parallel disposed to the rigid rod. A plurality of wire loops engage transverse processes on the convex side of a scoliotic curve and also engage a proximal one of the flexible rods. Tensioning of the flexible rods by the rigid rod produces a straightening force on the flexible rods and results in a straightening force on the vertebrae by means of forces exerted by the wire loops.
Posterior implantation apparatus has further included helical coil tension springs whose ends are connected to respective ones of vertebrae by metal hooks. This type of apparatus is known by the trade name Weiss and provides a degree of fixation for fractures and fracture dislocations of the spine.
The posterior implantation apparatus that has gained the greatest acceptance in that which comprises an elongated and rigid rod and two or more hooks that are hooked onto respective vertebrae and that are secured to the rigid rod. A pair of rods may be used with one rod and the hooks thereof providing a distraction force and the other rod and the hooks thereof providing a compression force. This general type of apparatus has been sold under various trade names but primarily under the trade name Harrington.
Finally, the prior art includes Lewis et al., U.S. Pat. No. 4,085,744, in which a plurality of flat straps are alternately interconnected by engagement of hook shanks and adjusting devices. The hooks may be connected to individual vertebrae for applying distraction or compression forces.